Sen. Ben Nelson of Nebraska is holding out mainly for tougher antiabortion language. Republicans halt debate temporarily by insisting that a 767-page amendment be read aloud.

Reporting from Washington — New obstacles slowed Senate action on the healthcare bill Wednesday, as the hunt for supporters narrowed to a lone Democrat -- Ben Nelson of Nebraska -- and Republican delaying tactics brought debate to a temporary standstill.

But Democratic leaders made progress toward bringing their party in line and remained hopeful that they would pass the bill through the Senate by Christmas -- just barely.

The effort to win Nelson's support hinges largely on abortion policy, the issue that nearly derailed action on the healthcare bill at the last minute in the House, where antiabortion Democrats insisted on tight restrictions on abortion funding under the proposed new health programs.

Nelson, seeking similar abortion restrictions, continued to withhold his support for the Senate bill despite major concessions made to him on other issues affecting the powerful insurance industry, which is important to his home state.

Efforts to address his abortion concerns advanced Wednesday as another antiabortion Democrat -- Sen. Bob Casey of Pennsylvania -- floated a compromise designed to strengthen guarantees that federal funds would not be used for abortion.

Democratic leaders were cautiously optimistic that if they could nail down Nelson's vote, they would have the 60 votes they needed to break the filibusters expected to be mounted by Republicans.

Senate aides calculate that if Republicans use every procedural roadblock available to them -- as they have promised -- Democrats may not be able to bring the bill to a vote before Christmas Eve.

The power and variety of Republican delaying tactics became clear Wednesday when GOP members brought debate to a halt by forcing the Senate clerk to read the entire text of a 767-page amendment by Vermont Sen. Bernie Sanders, an independent, to establish a government-run insurance plan that would replace the private insurance system.

The amendment was not expected to pass, and after the clerk had spent two hours and 43 minutes reading 139 pages of the bill -- to a chamber with only two or three senators present -- Sanders withdrew the amendment to allow debate to resume.

"We are going to do everything we can to make it hard to pass a bad bill," said Don Stewart, a spokesman for Senate Minority Leader Mitch McConnell (R-Ky.).

In spite of all the end-game maneuvering, however, Senate Majority Leader Harry Reid (D-Nev.) has yet to unveil the details of his final version of the bill, a far-reaching "manager's amendment" that will incorporate all of the elements of the bill that he has had to revise to garner support from everyone in his party's caucus.

The fundamental aims of the bill remain the same: to reduce the ranks of people without insurance, make coverage more stable and slow the growth of healthcare costs.

Reid has decided to drop the so-called public option -- a government-run health insurance plan included in the House bill -- because of opposition from Senate centrists like Nelson and independent Joe Lieberman of Connecticut.

Although liberals in the House have threatened to vote against the health bill if it comes back for final approval without a public option, Speaker Nancy Pelosi (D-San Francisco) signaled more clearly than ever Wednesday that she could accept a bill without the option -- if she were satisfied with other elements.

"It depends on what else is in the bill," she told reporters. "Our priority on the public option -- the emphasis was not on 'public.' The emphasis was on 'option.' "

The head count of Democratic senators who have committed to vote with Reid to end the Republican filibuster has mounted slowly but steadily. In a White House meeting with President Obama and other Democrats on Tuesday, Lieberman indicated that he was prepared to support the bill after Democratic leaders agreed to drop plans to expand Medicare to people as young as 55.

Nelson is the only Democrat that leaders are really worried they could lose. He welcomed the leadership's decision to drop the public option -- a provision bitterly opposed by insurance companies -- and Reid's assurance that the bill would not include a proposal to strip the insurance industry of its federal antitrust exemption.

But that was not enough to win Nelson's support. He still objected that the bill's provisions barring the use of federal funds for abortion did not go far enough to enforce the ban in the new insurance-buying exchange that would be set up for people who do not get insurance from their employers.

The Senate rejected Nelson's amendment to insert the House's stronger language, which would bar insurance companies in the exchange from covering abortion in policies for people receiving federal premium subsidies.

The Senate bill would allow those policies to cover abortion so long as they segregated the federal funds and guaranteed that only private premiums were used for the procedure.

But even as he and Democratic leaders considered compromise abortion language, Nelson told reporters in a conference call that abortion was not the only troublesome issue.

He said that he also was concerned about the bill's proposed new long-term care insurance program and cuts in Medicare payments to home healthcare providers.

"Until those things are corrected, it's not something I can vote for right now," he told reporters.